Manufacture of sulphuric acid by the contact process



` July 7, 1925. 11,545,142l

H. HOWARD MANUFACTURE OF SULPHURIC ACID BY THE CONTACT PROCESS Filed June 2. 19.24

Pyr/7E or 4 Br//msfone Bar/1er Cd/725er Wafer dem D Howard To all -wrlwm it' may concern:

man@ my' v, 1922.5. s

UNITED STATES "PATENT Lorsica.

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EANUFCTUBE 0F SULPHUBIC- ACID BY THE CONTACT PROCESS.

application aided :wie 2, it, serial no. 717,407.

Be it known that 1,-HENRY HoWAnv, a

. citizen of the 'United States residing at Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in the Manufacture of Sulphuric `Acid by the Contact Process, of which the following is a speci- .the contact process hot burner cation.

In' the process at presentcommonly used.

for the manufacture of'sulphuric acid by ases' containing sulphuric dioxid produce b burning sulphurous material such as brimstone or pyrite are prepared for treatment in the converters by being cooled, filtered, dried and then reheated to a suitable temperature for entry into the converters. For cooling the gases it is customary to use a so-called wetcooler, that is, a scrubbing tower in which the -hot gases are contacted with cool and relatively dilute sulphuric acid, and for filtering the cooled gases coke filters usually are employed. In case the gases have been cooled by meansl of a wet cooler, the lmpure acid separated therefrom by the iltersordinarily amounts to from 3 to 5% of the theoretical yield of sulphuric acid calculated on the quantity of sulphur burned.

The drying of the filtered gases is carriedV out by contacting'them with relatively concentrated sulphuric acid in' one or more scrubbing towers. The drying of the gases which have been cooled by scrubbing with dilute acid and filtered as described, requires in the neighborhood of 550 pounds of 66 B. sulphuric acid per ton of sulphur burned. This acid used for drying the gases, as Well as the impure acid separated by the -ilters, represent Very substantlal losses'in the process. 'If it is attemptedto avoid the use of drying acid in the process by cooling the hot burner gases in dry coolers, another5 difficulty is vencountered in that the gases may, under some circumstances, be so dry that the concentration of the impure acid `collected in the filters will be as high as B. which is too high for operating purposes, I have now found that by dry-cooling the burner gases and theni conditioning them with respect to their moisture content to a point intermediate the saturation point and the point at-which impure acid of a concentration of 4\5 B. 1s

after drying them to.. a point suitable forV conversion, 'the yield of impure acid and the Bowman, or CLEVELAND, omo, smartcard 'run caassmr enmarcan COMPANY, cr cLavELANnjonvIo, a concurren or omo."

drying acid requirements may be very matei rially reduced and at the'same .time the separation of impure acid of to hi ha concentrationin the coke iilters is avoided.. l

n For convenience in describing my inveni tion reference -1s made to the accompanying drawin in which the single fi re 1s a iow sheet vo a contact sul huric acid plant with the converters and su sequent parts omitted.

Referring to the drawing A represents a burner for rimstoner pyrites or other sul-A p hur containing material and B represents either a dust chamber in case pyrite is burned or a combustion chamber in case brimstone is burned. C represents a preliminary cooler which preferably is a sys-- tem of alr cooled pipes or conduits and is of course of the dry cooler type. The Howard cooler marked D constitutes the subject matter of my copending application Serial No. 594,112, iled October 12, 1922. This cooler also is of the -so-called dryy cooler type and 'comprises a relatively large o en chamber having water cooled side wa s. E represents a tubular cooler, that is, a cooler` formed of pipes or conduits which are submerged in a water bath or kept wet b water sprays. rlhis cooler E also is of t e drycooler type. F and G represent coke filters, H represents one or more drying towers, and I represents a spray catcher, all of the usual type.

In carrying out the process in accordance with my invention the hot burner gases leaving the. dust'chamber or combustion chamber as the case may be at a relatively high temperature, s'ay 1400 F., pass to the pre' liminary cooler C in which their temperature is reduced'to about 800o F., then into the cooler D where their temperature isreduced to say 300 F. and then into the tubular cooler E in which the temperature is reduced to say 100 F. At some point in the flow of the gases following their passage through the preliminary cooler C and before `their passage through the coke filters F and cus` other suitable way, at one or more points in their path between the lpreliminary cooler C and the coke filter On the accompanying flow sheet theA introduction of a water spray at the entrances to the cooler D and the coke filter F is indicated. The introduction of at least a part of the required amount of water at the entrance to the cooler D serves to dilute the acid which collects in the ues directly following it and thus to prevent their corrosion. Introduc- 4 tion of moisture into the coke filter F has been found to give the most uniform and satisfactory results. The es are then passed through the coke iiters F and G and then dried and heated for delivery to the converters. The pur ose of the preliminary dry cooling of t e gases is to reduce the temperature of the relatively dry hot burner ases to a temperature below which a relative y high moisture content will not result in the formation of sulphuric acid. In this way the excessive production of impure acid, as is the case when a wet cooler is employed, is avoided. lAfter the gases have been preliminarily or referably wholl cooled they are moisteneg or conditions with respect to their moisture content to a proper degree for filtering. In conditioning the gases with respect to their moisture content two factors must be taken into consideration. .The moisturel content lof th'e ases should be made as small as is possible 1n order to minimize the drying acid requirements and on the other hand the. gases must contain suiiicient moisture so that the concentration of the impure acid collected in the filters will not -be excessive. lAs is stated above, the limits of the moisture content of the gases entering the filters are from saturation on the one hand to a moisture con tent capa-ble of producing impure acid o 45 B on the other hand. In practice have found that the moisture content should be sufficiently high to give impure acid of not more than 30o B and preferably between 20 and 25 B. The coolers D and E serve to reduce the temperature of the vases delivered from the preliminary cooler to a temperature suitable for filtering, say under 100 F. The gases after bei cooled in a dry state and then conditione with respect to their moisture content are filtered in the usual way', preferably through a plurality of coke filters. The qu-antity of impure acid separated from the gases is practically negli 'ble' amounting to only about 0.3 to 0.6% o the total theoretical yield, this result being attributed to the cooling and conditioning of the gases in the manner described. The gases are next dried in the usual way -by means of drying towers through which strong sulphuric acid is circulated. However, due to the relative absence of `moisture in the gases during .the

cooling step as comgred with moistening which takes place w en the hot subjected to wet cooling as in t e prior process referred to, the coolin is vmuch more easily and completely accomp ished, thereby reducing the dr Aing acid requirements from about 550 poun s of 66 B acid per ton of sulphur burned in a plant using the said prior process to about 175 pounds of 66 acid per ton of sulphur burned in m process. The gases leaving the drier pass through the spray catcher I, the construction and operation of which are well known, and then to the converters and subsequent .parts of the contact sulphuric acid plant which form no part of the present invention.' y

The drying of the gases of course is for the purpose not only of reducing the moisture content thereof to the most desirable point for the converting step, but also to prevent thepremature formation of H,SO in the iron apparatus which would result in its corrosion.

My process therefore is a compromise between two extremes, that is, between wet cooling ofl the burner gases followed b ltration and the incidental production o relatively large amounts of impure acid and then the drying of the gases using relatively large quantities of ing acid on the one hand, and the dry cooling of the burner gases followed directly by filtration with the separation of impure acid of too high a concentration for satisfactory o ration with coke filters and then humidi ying the filtered gases for the purpose -of establishing a proper moisture content for the convertingstep 4on the other'hand.

In the foregoing description I have described a preferred form and arrangement of apparatusl and a preferred procedure to be-followed in carrying out my invention. It is to be understoo however that the practice of the invention is not limited to the -use of the particular apparatus or to the 1. In a process of making sulphuric acid the steps comprising,A cooling hot burner gases out of contact with water, moistening the cooled gases and thereafter successively filtering and drying the gases,

2. In a process of making sulphuric acid the steps comprising, cooling hot burner gases out of contact With Water, and moistcnng the cooledgases to a point intermediate saturation thereof and a point at which acid of a concentration of 45 B. may be separated therefrom.

3.7111 a process of making sulphuric acid the steps comprising, cooling hot burner gases out of contact with Water and moistcning the cooled gases to a point intermediate saturation thereof and a point at which acid separated therefrom has a concentration not greater than 30o B.

il. In a process of making sulphuric acid the steps comprising, cooling hot burner gases out of Contact with Water, and moisttoning the cooled gases to a point at Which acid separated therefrom has a concentration of about 20-25o B.

5. In the contact process for the manufacture of sulphur-ic acid the steps Which consist in cooling hot burner gases out of contact with water, conditioning the cooled gases With respect to their moisture content to a -point intermediate saturation and a humidity at which acid of 45 B may be separated therefrom, filtering the cooled and conditioned gases, drying the filtered gases to a humidity suitalole` for conversion and heating the dried gases to `a temperature suitalole for their introduction into the converter.

In testimony whereof,lI aiix my signa- 

